It seems like there must be some kind-of standard for sizing that exists, at least for use within the industry. But (and I've given this a lot of thought in the past) clothing designers then choose to assign random numbers to those sizes that are relative only to each other within that brand. So while I could be a size 0 in one brand, I could easily wear a 4 in another, etc. I think this "relative sizing" (my term) is much more prevalent in younger women's clothing, as the more I shop for professional attire the more the sizes seem to correspond across brands. Then, this would make the ability for women to identify with a particular size a realistic conception of themselves.

Also, I totally remember the Sweet Valley High books. I think that if they were written today, the twins would no longer be a size 6. In today's world teens have the Lindsay Lohan's to compete with and compare themselves to.